Armrest for chair of spa foot bath



FIG. 1 is a front perspective view of an armrest for chair of spa foot bath showing my new design;

FIG. 2 is an enlarged front perspective view of the armrest shown in isolation; and,

FIG. 3 is a side view thereof.

The broken line showing the remainder of the chair and spa foot bath in FIG. 1 is for illustrative purposes only and forms no part of the claimed design. The unshown portions of the armrest form no part of the claimed design. 

The ornamental design for an armrest for chair of spa foot bath, as shown and described. 